You’re missing a couple key things to consider with this solution.
If you want to group with a friend that’s in a different layer, now you have to choose between being able to gather resources for your profession or gold and playing with your friend. Not a good choice to make.
As for the lockout: maybe one of your friends on a different layer needs help with a kill quest. If you want to help them, now you’re forced to sit around for 5 minutes until you can group into their layer. God forbid you’re in STV and happen to get ganked. Combat happened, timer reset. Wait another 5 minutes. And again. And again. Maybe you could just hearth/fly back to a capital. That’s dandy, but now you also factor in the 5 minute wait, plus whatever travel time to get to your friend.
Way too many negative repercussions for the “problem” it would fix. I put problem in quotes because AFAIK the layering system won’t be permanent. It’s a short term solution for the masses during release. Tbh I would rather let players abuse the hopping for a couple weeks at release than see the solutions you suggested be implemented.